1. Field of the Invention
The present invention relates to a liquid ejection head ejecting a desired liquid by utilizing bubble generated by acting a thermal energy on the liquid, a head cartridge and a liquid ejecting apparatus employing the liquid ejection head, a fabrication process of the liquid ejection head, a liquid ejecting method, a printing method and a printed product obtained by utilizing the liquid ejecting method. The present invention further relates to an ink-jet kit having the liquid ejection head.
Particularly, the present invention relates to a liquid ejection head having a movable member displaced by utilizing generation of bubble, a head cartridge and a liquid ejecting apparatus employing the ejecting head. The present invention relates to a liquid ejecting method and a printing method ejecting a liquid by displacing the movable member utilizing generation of bubble.
Furthermore, the present invention is applicable to a printer performing printing on a printing medium, such as paper, yarn, fiber, cloth, leather, metal, plastic, glass, wood, ceramic or the like, a copy machine, a facsimile machine having a communication system, a word processor having a printing portion and the like, and further to an industrial printing apparatus which is able to compose to various processing devices.
It should be noted that, in the present invention, a word "print" not only means forming a meaningful image per se, such as character, drawing and the like, but also means forming a meaningless image, such as a pattern.
2. Description of the Related Art
Conventionally, so-called bubble-jet printing method has been known as an ink-jet printing method. The method comprises the steps of providing an ink with an energy such as a thermal energy to cause abrupt volume variation (generation of bubble) of the ink, and of ejecting the ink through ejection ports by an acting force on the basis of the state variation to deposit the ejected ink on a printing medium to form an image. In a printing apparatus employing the bubble-jet printing method, ejection ports for ejecting the ink, ink passages communicating with the ejection ports, and electrothermal transducers as energy generating means for ejecting ink in the ink passages are typically arranged as disclosed in U.S. Pat. No. 4,723,129 and the like.
With such printing method, high quality image can be printed at high speed and low noise. A printing head implementing this method has many merits that high resolution image and color image can be easily obtained because the ejection ports for ejecting the ink can be arranged at high density. Recently, the bubble-jet printing method has been employed in a large number of office use apparatus, such as printers, copy machines, facsimile machines and the like, and is also applicable to industrial system, such as a textile printing apparatus.
According to spreading of application of the bubble-jet technology in various kinds of products, the following demands are recently growing:
For example, optimization of a heater as energy generating means is studied in order to demand for improvement of an energy efficiency. As the optimization of the heater, adjustment of a thickness of a protective layer for standing between the heater and the ink can be nominated. This method is effective for improvement of a transmission efficiency to a generated head to the liquid such as the ink.
On the other hand, in order to obtain high quality image, there has been proposed a driving condition for providing the liquid ejecting method or the like enabling high speed ink ejection and ink injection in good condition based on stable bubble generation. Also, in viewpoint of high speed printing, there has been proposed a printing apparatus with an improved liquid passage configuration for obtaining the liquid ejection head having high speed re-fill. Here, "re-fill" means liquid supply from the common liquid chamber to ejection ports through liquid passages when liquid is ejected from the ejection port to generate negative pressure near the ejection port in the liquid passage or when bubbles in the liquid shrinks after the pressure generated on growth of the bubbles are utilized for ejection of the liquid.
Among the liquid passage configuration, the flow passage structure as shown in FIGS. 48A and 48B has been disclosed in Japanese Patent Application Laid-Open No. 199972/1988. The disclosed liquid passage structure and the head fabrication method are inventions work out in view of a back wave generated associating with generating of the bubble. The back wave is generated by pressure directed toward opposite direction to a direction toward the ejection port, namely a pressure directed to a liquid chamber 12. The back wave is not an energy directed in an ejecting direction and thus is known as a lost energy reducing an ejecting energy.
FIGS. 48A and 48B disclose a valve 10 located at a position away from a region, in which the bubble is generated by the heater 2, and at opposite side to the ejection port 11 with respect to the heater 2.
In FIG. 48B, the valve 10 has an initial position attached to an upper plate as a ceiling of the liquid passage 3. Associating with generation of bubble, it hangs down into the liquid passage. This invention is disclosed to restrict energy loss by controlling a part of the back wave by means of the valve 10.
However, in the shown construction, as can be appreciated from study for behavior of the liquid upon generation of bubble in the liquid passage retaining the liquid to be ejected, it is not practical to restrict a part of the back wave by means of the valve for ink ejection.
In nature, the back wave per se is not directly associated with ejection as set forth above. When the back wave is generated within the liquid passage 3 as shown in FIG. 48A, a pressure directly associated with ejection of the liquid is already places the liquid from the liquid passage 3 in condition permitting ejection thereof. Accordingly, even when a part of the back wave is restricted, no significant effect may be provided for ejection.
On the other hand, in the bubble-jet printing method, since the heater repeats heating in a condition contacting with the ink, a deposit due to baking of the ink is generated on the surface of the heater. In certain kind of the liquid or ink, large amount of deposit is generated to make generation of bubble unstable. Also, when the liquid to be ejected has a property to be easily degraded the quality by heat, or when the liquid is difficult to obtain sufficient bubbling, it has been desired to provide a method to achieve good ejection without causing change of property of the liquid to be ejected.
In such viewpoint, a method to use a liquid (bubbling liquid) to generate bubble by a heat, which is different from a liquid (ejection liquid) to be ejected, to transmit a pressure generated by bubbling to the ejection liquid to perform ejection, has been disclosed in Japanese Patent Application Laid-Open No. 69467/1986, Japanese Patent Application Laid-Open No. 81172/1980, U.S. Pat. No. 4,480,259 and so on. In these publications, an ink as the ejection liquid and the bubbling liquid are completely separated by a flexible membrane formed of a silicon rubber or the like so that the ejection liquid may not contact with the heater directly, and pressure generated by bubbling of the bubbling liquid is transmitted to the ejection liquid by deformation of the flexible diaphragm. By such construction, prevention the surface of the heater from being deposited, improvement of freedom in selection of the ejection liquid and so on can be achieved.
However, in the ejection head having a construction, in which the ejection liquid and the bubbling liquid are separated completely as set forth above, since the pressure generated by bubbling of the bubbling liquid is transmitted to the ejection liquid by expanding and contracting deformation of the flexible diaphragm, the pressure of the bubbling can be absorbed by the flexible diaphragm in significant extent. Also, magnitude of deformation of the flexible diaphragm is not so large. Therefore, while it is possible to separate the ejection liquid and the bubbling liquid by the flexible diaphragm, it is possible to lower energy efficiency and ejection force.
It is necessary to elevate a basic ejection characteristic to a high level unpredictable from the conventional technique, the conventional level being obtained by a conventional method comprising the steps of forming a bubble within a liquid passage (particularly, a bubble generated by a film boiling) to eject the liquid.
In order to elevate such level, it is necessary to return to a principal for liquid ejection, and to develop a new method for ejecting a liquid and a new liquid ejection head performing such a new method, the method using a bubble which can not be obtained by the conventional technique. Here, a movement of a movable member within a liquid passage is analyzed as a starting point to obtain a first technical analysis which analyzes a principal mechanism of the movable member with the liquid passage. A principal of liquid ejection by a bubble is analyzed as a starting point to obtain a second technical analysis. A bubble forming region is analyzed as a starting point to obtain a third technical point.
Because of these analyses, a new technique for controlling the bubble positively can be established that the free end of the movable member should be arranged at the ejection port side or at the downstream of the liquid flow within the liquid passage, and that the movable member should be arranged opposing the thermal energy generation device or the bubble generation region.
Considering quantity of the ejected liquid which is influenced by the bubble per se, it is realized that the consideration of component of the bubble growing toward the downstream is the biggest element in order to extremely improve the ejection characteristics. In other words, it is found that the efficient conversion of the component of the bubble toward the ejection direction serves to improve the ejection efficiency and the ejection rate. Therefore, it is noted that the new technique level is higher than the convention technique level because the new technique positively leading the downstream component toward the free end of the movable member.
Furthermore, it is preferable to consider structural elements such as the thermal generation region for forming the bubble, for example, the downstream side with respect to a line passing a center of area of one surface relating to liquid flow direction of the electro-thermal transducer, or the movable member and the liquid passages relating to the downstream side of bubble growing with respect to a line passing a center of area of one surface relating to the bubble generation.
On the other hand, it is found that a re-fill rate can be improved by considering the arrangement of the movable member and the structure of the liquid supply passage.
The applicant has already been file the patent application the excellent principal of the liquid ejection on the basis of the knowledge obtained by the investigation and the study as described above and the total viewpoints. The present invention has been made by the inventors on the basis of their preferable idea as a premise of such liquid ejection principal.
Several points which are acknowledged by the inventors are as follows:
In the liquid ejection head as described above, after the liquid ejection method is not performed at a long period, it is considered that the ejection ports are clogged up by virtue of the high viscous ink and dusts. In the case, it prevents the ejection liquid from the preferable ejection, and also it prevents the liquid from the preferable ejection because the bubbles are generated within the liquid of the second liquid passage. These problems must be avoided or instantly removed. Furthermore, in the liquid ejection method as described above, in case of using two liquids, namely the ejection liquid and the bubbling liquid, after the liquid ejection method is not performed at a very long period, it is considered that the ejection liquid and the bubbling liquid are slightly admixed. Since a preferable printing is influenced in such cases, these cases must be avoided or instantly removed. The recovery of the difficulty ejection is performed by pressurizing and/or sucking the liquid within the liquid passage. In this case, it is important that the recovery is not sufficient by virtue of the flow resistance in the respective passages.